| Title | Structural studies of monoamine oxidase (MAO) |
| Time frame | 1997-2001 |
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| Background | Monoamine oxidase (MAO) is important in the metabolism of aromatic amines, including neurotransmitters such as serotonin, adrenaline, histamine and dopamine. The first modern antidepressants were irreversible and unspecific inhibitors of MAO, but due to their adverse side effects they fell into disuse. After the finding that the enzyme occurs in two isoforms, MAO-A and MAO-B, the interest in the development of isoform-specific MAO inhibitors (MAOIs) has evolved. The therapeutic effects of MAOIs fall into two categories. MAO-A inhibitors have been used mostly in the treatment of mental disorders, in particular depression. The only MAO-B inhibitor which has been extensively tested in human disorders is L-deprenyl. This drug has some positive effects in the treatment of both neurological disorders, e.g. Parkinson¹s and Alzheimer¹s disease, and also in clinical depression. There is still a need for further development of these inhibitors. Therefore knowledge of the three-dimensional structures of MAO-A and -B could have a significant impact on the rational (structure-based) design of novel inhibitors, potentially with therapeutic applications. |
| Progress | We have worked with different systems to try and obtain large quantities of protein of a quality suitable for crystallisation. MAO-B was purified from bovine liver mitochondria using published protocols. It is possible to get large quantities, but not with adequate quality due to aggregation problems. In collaboration with Professor J.C. Shih and her group at USC, Los Angeles, USA, we expressed a full-length and a C-terminal-truncated human MAO-A construct in Sf21 cells using the baculovirus system. However, these recombinant proteins also aggregate. In the absence of a crystal structure, we have previously constructed a homology model of MAO. This model has been used to design mutants with the goal to get a more soluble but still active protein. Mutants have been cloned and expressed in E. coli. The construct was made such that it could easily be transferred to a vector for expression in Pichia pastoris. No large amounts of soluble and pure protein for crystallisation have been obtained. Since Binda et al. have recently solved the structure of MAO-B this project will be discontinued. |
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| Remarks | An older page about MAO can be found here. |